Related fields include Related fields include thin-film formation by atomic layer deposition (ALD), chemical vapor deposition (CVD), and related techniques; in particular, formation of compound nitrides of components with differing reaction temperatures.
Advanced thin-film devices can only benefit from new materials if those materials can be reliably produced. Oxides, nitrides and oxynitrides of mixed materials show promise, for example, as variable-resistance and constant-resistance layers of resistive-switching memory (sometimes called “ReRAM”), and in other applications. In some of the applications, stoichiometric oxygen and/or nitrogen content is desirable; in others, non-stoichiometric variations are preferred. However, some of these complex compounds can be difficult to deposit or grow in the desired ratios of the different elements.
Various nitrides have been considered for various components of ReRAM cells, in particular for embedded resistors because of their stable performance and tunable resistance characteristics. However, deposition of nitrides usually requires elevated temperatures that may be damaging to other cell or circuit components. Furthermore, the high temperature requirement limits the selection of the precursors that may be reacted with nitrogen containing precursors during deposition of nitrides.
For example, consider tantalum silicon nitride (TaSiN). With fairly high Si content, it works well as an embedded resistor in a ReRAM stack. However, the Si precursor tris(dimethylamino)silane (TDMAS) will only react with the N precursor NH3 to form SiN at a process temperature greater than 500 C, while the Ta precursor (tert-butylimido)tris(diethylamido)tantalum(V) (TBTDETa) decomposes at temperatures above about 340 C. This disparity in tolerable temperature range poses serious obstacles to conventional co-deposition.
Therefore, a need exists for a way to form metal silicon nitrides with sufficiently high silicon-nitride content for embedded resistors without exceeding the process temperatures tolerated by the metal precursors; for example, by using a non-thermal type of energy to promote the silicon-nitride reaction. Plasma has been used, but may be inconvenient because of the specialized equipment needed.